Metapleural Transformations with Respect to Propodeum and Metapostnotum in Hymenoptera

Abstract

In Symphyta the metapleural suture is prominent and the epimeron is continuous with the metapostnotum through an epimeropostnotal bridge. However, in Xiphydridae and Siricidae the bridge and the metapostnotum are considerably reduced. In Hymenoptera Parasitica the pleural suture has become marginal thus obliterating the epimeron and narrowing the bridge. In aculeatans (Chrysididae, Scoliidae and Sphecidae) this bridge and the metapostnotum are untraceable and the episternum becomes subdivided into 2 portions. Similar conditions occur in Vespidae, Eumenidae, Apoidea and winged forms of Formicidae except that the posterior half of the pleural suture has lost its identity. In Pompilidae secondary modifications of the metapostnotum are prominent and the bridge is conspicuous. In non-winged forms of Formicidae and female Mutillidae the bridge, metapostnotum, and the pleural suture are absent. These changes can be helpful in establishing the relationships among the various hymenopteran families.